Conventional display panels and display devices using electrochromic materials have utilized such materials as solutes in liquid electrolytes. Generally the solvent is water to which is added a metal salt to provide conductivity. Glycerine and ethylene glycol solutions have also been used, each containing an organic electrolyte as the electrochromic material and a metal salt or the like to provide adequate conductivity.
Wherever liquid materials are used in a display panel, it is necessary to use spacers and sealants in order to avoid leakage and consequent failure of the device. In general, it has been necessary to make the walls of the display device relatively thick and to make the liquid layer relatively thick both for reasons of strength and to provide the required display intensity.
Naturally, substitution of ethylene glycol or glycerol for water as the solvent increases the viscosity of the solution but, even so, leakage remains a problem, particularly where the conditions of use may be severe. Consequently, it would be extremely desirable to provide electrochromic display devices and panels which are completely free of liquid components.